Pulmonary embolism (PE) is a sudden blockage of one or more arteries in the lungs by a blood clot, usually traveling from deep veins in the legs or pelvis, and it can cause cardiac arrest within minutes if untreated. In India, this life-threatening condition remains substantially underdiagnosed due to limited public awareness, incomplete recognition among some clinicians, and the mistaken belief that PE is primarily a Western disease.

What Is the Connection Between Leg Clots and Lung Clots?

Deep vein thrombosis (DVT) and pulmonary embolism are two stages of the same disease, called venous thromboembolism (VTE). DVT occurs when a blood clot forms in a deep vein, most commonly in the calf, thigh, or pelvis. When a piece of that clot breaks free and travels through the bloodstream to the right heart and into the pulmonary arteries, it becomes a pulmonary embolism.

DVT typically presents with one-sided leg swelling, pain, tenderness, and redness. However, a significant proportion of DVT cases are silent, meaning patients have no symptoms until a piece of the clot breaks off and reaches the lungs. Any asymmetric leg swelling in someone with risk factors deserves urgent medical evaluation.

What Are the Warning Signs of a Pulmonary Embolism?

Pulmonary embolism symptoms vary depending on the size of the clot and the patient's heart and lung health. The most common warning signs include sudden unexplained breathlessness, which often appears abruptly without an obvious cause. Any acute onset of breathlessness in someone with PE risk factors must be evaluated urgently.

Additional symptoms to watch for include:

• Pleuritic chest pain: Sharp chest pain that worsens when breathing or coughing, caused by inflammation of the lung lining near the clot.
• Rapid heart rate: A fast heartbeat is nearly universal in significant PE and reflects the cardiovascular stress of reduced blood flow to the lungs.
• Coughing up blood: Blood-tinged sputum can occur when a segment of lung tissue loses its blood supply.
• Dizziness or fainting: These symptoms indicate that the heart is severely strained and blood pressure is dropping dangerously.

In massive PE, a large central clot causes dramatic symptoms including severe breathlessness, low blood pressure, pale skin, bluish discoloration, and potentially cardiac arrest. This constitutes an extreme emergency requiring immediate hospital transfer and, in appropriate cases, emergency mechanical intervention.

Who Is at Highest Risk for Blood Clots?

Certain factors significantly increase the risk of developing venous thromboembolism. These risk factors are highly prevalent in India's patient population and often occur together in the same person.

• Prolonged immobility: Extended bed rest, hospitalization, or long-haul flights prevent normal blood circulation in the legs.
• Recent major surgery: Hip and knee replacement surgeries carry particularly high risk for blood clot formation.
• Active cancer: Cancer and cancer treatments increase the body's tendency to form clots.
• Pregnancy and hormone use: Pregnancy and oral contraceptives or hormone therapy alter blood clotting factors.
• Obesity: Excess weight increases inflammation and clotting risk.
• Inherited blood clotting disorders: Some people are born with genetic conditions that make their blood clot more easily.

How Do Doctors Diagnose a Pulmonary Embolism?

Diagnosis begins with clinical assessment using validated scoring tools like the Wells PE Score, which quantifies the likelihood of PE based on symptoms, physical findings, and risk factors. In patients with low to intermediate probability of PE, a D-dimer blood test can safely rule out the condition if the result is negative.

For patients with high probability of PE or those who cannot be safely ruled out with blood tests, CT pulmonary angiography (CTPA) is the gold standard imaging test. CTPA directly visualizes clots in the pulmonary arteries, shows how much of the lungs are affected, and reveals whether the right side of the heart is strained. In hemodynamically unstable patients who cannot be safely transported for CTPA, echocardiography provides rapid bedside assessment of right heart function.

How Is Pulmonary Embolism Treated?

Treatment depends on the severity of the PE. Low-risk PE, defined as normal blood pressure with no evidence of right heart strain, is treated with anticoagulation therapy, which prevents clots from growing and new clots from forming. Direct oral anticoagulants (DOACs), particularly rivaroxaban and apixaban, are now first-line treatment and allow most low-risk patients to be managed at home or with brief hospitalization.

Submassive PE, characterized by normal blood pressure but evidence of right heart dysfunction on imaging or echocardiography, requires close monitoring and anticoagulation, with selective use of catheter-directed therapy for patients who worsen or are at high risk of deterioration.

Massive PE with hemodynamic collapse is a medical emergency requiring immediate restoration of blood flow to the lungs. Systemic thrombolysis, which involves intravenous clot-dissolving medications, is the primary intervention when not contraindicated by bleeding risk. When systemic thrombolysis is unsafe or ineffective, mechanical thrombectomy becomes life-saving.

What Is Mechanical Thrombectomy and When Is It Used?

Mechanical thrombectomy is an advanced interventional procedure for high-risk PE that does not respond to standard treatment. The procedure involves navigating a catheter through the femoral vein, through the right heart, and into the pulmonary arteries, where specialized devices physically remove or fragment the clot and restore blood flow without the systemic bleeding risk associated with intravenous clot-dissolving drugs.

Large-bore aspiration thrombectomy systems and ultrasound-facilitated catheter-directed thrombolysis are the principal techniques used. This advanced intervention requires specialized training, a dedicated catheterization laboratory team, and rapid mobilization of a multidisciplinary PE Response Team. This capability is now available in select centers in India, offering patients with high-risk PE access to the most advanced treatment options.

Steps to Take If You Suspect a Pulmonary Embolism

• Seek immediate emergency care: Any combination of sudden unexplained breathlessness, rapid heart rate, and recent leg swelling requires immediate medical evaluation. Do not delay.
• Inform your doctor of risk factors: Tell emergency personnel about recent surgery, long flights, cancer diagnosis, pregnancy, oral contraceptive use, or prolonged immobility.
• Request PE-specific testing: Ask whether D-dimer blood testing or CT pulmonary angiography is appropriate for your clinical situation.
• Follow anticoagulation therapy: If prescribed blood thinners, take them exactly as directed and attend all follow-up appointments to monitor treatment effectiveness.

Improving awareness of pulmonary embolism, including who is at risk, what symptoms to recognize, and what treatment options are available from qualified specialists, is genuinely life-saving. Diagnostic delays cost lives, making rapid recognition and access to appropriate care essential.